There are known lift trucks for transporting stacks of tires that include a very long arm capable, in the horizontal position, of being inserted through the center of a horizontal stack of tires, and of picking up this stack with a subsequent vertical pivoting of the arm carrying the horizontal stack, so that the stack is vertical for transport.
It is understood that, in such a configuration, the stack of tires completely blocks the driver's field of vision in the truck's line of travel, forcing the operator to lean over or turn around (ergonomic problems) or to open up his field of vision by driving in a more or less “meandering” motion, which is not entirely safe. Often, if the width of the load is too large, the operator is forced to drive the vehicle in reverse, turning himself around (“rear facing” position). All of these stopgap measures are dangerous and/or pose serious ergonomic problems and fatigue.
The document DE 101 27 949 C2 discloses a pallet lift truck comprising two sets of two forks, each made to carry a pallet of merchandise, such that between the two pallets, in operation, a viewing space can be provided for the operator. But this truck cannot be used to transport stacks of tires.
There is therefore an important and recognized need for a lift truck that would make it possible to transport, load, unload, and perform other similar operations on stacks of tires with the operator in the “forward facing” position, and that would provide the operator with good visibility in the truck's longitudinal direction of travel and in a certain useful angle on each side of this longitudinal direction.
Naturally, such a truck should not include any mechanical means that might damage the tires, for example by excessive deformation, or even simply leave marks on their treads or sidewalls, which may cause the customer to return the tires on receipt.
Moreover, it would be interesting to link these advantages to an increase in productivity, i.e. in the number of tires transported per time unit over a given route. In this respect, the limits are currently reached quickly due to the fatigue associated with the operator's poor driving position.
It is therefore clear that the problem of safety and fatigue is linked to that of increasing productivity.
Hereinafter, “vertical” stacks designate vertical or roughly vertical stacks, the stacks of tires not necessarily being absolutely vertical. As a general rule, they are practically so, but a few degrees of inclination will not affect the invention. A larger inclination would not affect the use of the invention either, but would encounter problems with larger overhang and wasted space due to the inclination of the bottom tire. Except in the particular case of a very low shop ceiling, these situations are unlikely. Hereinafter, only the term “vertical” will be used, it being emphasized that this term covers the above options.
“Safe distance” designates herein the distance in front of the truck, i.e. in its direction of travel, beyond which it is reasonably necessary for the operator's field of vision to include a view of the floor so that for example he can stop safely if he detects an obstacle, and inside of which, when the truck is in continuous motion—i.e. not in the start or restart phase—at a normal speed, it is not necessary for the operator's field of vision to include the floor. It is understood that this simple term denotes the fact that on startup, and with each restart, the operator must verify that there are no obstacles inside of the safe distance—this is essential—but that, in continuous forward motion, the field of vision will make it possible to “scan” the floor and the space ahead of the truck from said “safe” distance forward.
Moreover, “horizontal” designates the direction perpendicular to the vertical direction. Naturally, the terms “vertical” and “horizontal” include the directions that are not exactly vertical or horizontal but close enough to these directions not to affect the balance of the vehicle.
“Upper” designates the upper part of the stack and the various elements of the truck, and “lower” designates the lower part.
“Internal” or “inner” designates the space located between the grasping means of a handling truck, particularly forks and clamps and arms, or the faces of certain elements turned or directed toward the “internal” space.
“Front” designates anything at the front of the truck, or in front of the truck, or the face of an element turned or directed toward the “front”
“Mast” designates the vertical fastening or guide elements mounted on any truck of the type in question, and capable of receiving, in a known way, loading means attached to guide carriages that can be height-adjusted on said “mast.” The mast has the reference 11 in the attached drawings.